Brain disorders in dogs and cats
The anatomy of the dog brain
Brain disorders in pets - an overview
The brain has a number of vital functions in the body, and damage to the brain for any reason can lead to severe disruption in the way an animal functions. To understand how diseases of the brain can lead to problems, it is first necessary to understand a little bit about what the different parts of the brain do. For most purposes, the brain can be divided into the forebrain, the brain stem and the cerebellum.
The forebrain is primarily made up of the cerebrum, and is involved in thinking and reasoning. A lot of processing of information occurs in the cerebrum, such as collating the messages from the senses and sending out signals to the muscles and other organs to react to those messages. Disorders of the forebrain therefore lead to problems with co-ordination and behaviour, so an animal with a disease affecting the forebrain may show signs of depression, aggression, aimless wandering and crying. In addition seizures (epilepsy) are a common feature of forebrain disease.
The cerebellum is concerned with the fine tuning of movement. Disorders of the cerebellum often lead to a tremor, and a characteristic high stepping gait, which is the animal overreaching as it walks, because of lack of fine control from the cerebellum.
The brain stem receives messages from many of the nerves of the head such as those controlling balance, sensation to the face and the muscles of the head. It also has a vital role in maintaining consciousness, and in breathing. Disorders of the brain stem can therefore lead to problems with balance, manifested by a head tilt, nystagmus (flickering of the eyes which is experienced by the individual as room spin) and wobbliness, paralysis of the muscles of the head and in the worst cases coma and death.
Diseases affecting the brain
The brain can be affected by processes that originate within the skull (intra-cranial) or outside the skull (extra-cranial). Extra-cranial problems include toxins such as metaldehyde and lead which can affect the brain when ingested. Toxins created by dysfunction of the body, such as in liver failure (causing a condition called hepatic encephalopathy) can lead to signs such as depression and seizures. Other metabolic diseases might lead to low blood glucose or low blood calcium which can also affect the brain and cause seizures. Diseases that occur within the brain include tumours, strokes, infections and inflammatory conditions. Some diseases don't have an obvious underlying cause, and are termed "idiopathic". The most common type of epilepsy, which affects young dogs, is usually idiopathic, although it is suspected that in some cases there is a genetic influence.
The brain is a fantastically complicated structure, and problems throughout the body can affect it. Symptoms of brain disease can vary greatly depending on the part affected. A detailed physical examination by an experienced vet can often help localise where the problem is, but advanced tests such as MRI scans and spinal fluid analysis may be needed to make a diagnosis.
NOTE - the internet is not a substitute for a vet. If you think your animal is ill, please seek qualified veterinary advice.
Books by the author
- The Nervous System of Dogs and Cats
This article gives an overview of the different parts of the nervous system in dogs and cats, what they are for, and what happens when they go wrong.
- What causes epilepsy in dogs?
There are a large number of causes of fits (seizures) in dogs, and this article describes the most common ones, and how they are diagnosed.
- Neurological Problems of Cavalier King Charles Spaniels
MRI scan of a Cavalier King Charles Spaniel with hydrocephalus. The Cavalier King Charles Spaniel is one of my favourite breeds of dog to see in my surgery. They seem invariably to have a happy temperament,...
- MRI in veterinary medicine
MRI stands for magnetic resonance imaging. It is a type of imagine that relies on magnets, rather than ionising radiation, as is produced by x-ray machines and CT scanners. MRI relies on powerful magnets that...